Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Feb 24 2023 12:54:12 ACUS01 KWNS 241254 SWODY1 SPC AC 241252 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0652 AM CST Fri Feb 24 2023 Valid 241300Z - 251200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF COASTAL SOUTHERN CALIFORNIA... ....SUMMARY... A brief tornado is possible over parts of coastal southern California. ....Synopsis... In mid/upper levels, positively tilted, synoptic-scale troughing extends from southwestern Canada across the Pacific Northwest and through a strong cyclone centered offshore from Cape Mendocino. The associated 500-mb low is expected to move generally southward through 06Z, taking it farther offshore from the mainland, before turning southeastward between 06-12Z. By the end of the period, the low should be located about 275 nm west of LAX, with cyclonic flow covering the western Great Basin, western AZ, northern Baja, and all of CA. Over southern CA, height changes will be minimal through most of the day, due to pivoting of the gradient as the cyclone digs offshore, but height falls are likely overnight once the low track assumes an eastward-directed component. Farther east, synoptic-scale mid/upper ridging will amplify by 12Z from northern UT southeastward over west and south TX, connecting to a persistent, large-scale, subtropical ridge that extends from north-central TX eastward over the length of the Gulf, through a high in the FL Keys/south FL vicinity, to the Bahamas and Atlantic waters still farther east. Low-level warm advection, moisture transport, and related ascent to LFC will support episodic thunder potential from the Mid-South across parts of MS/AL/GA to coastal SC. This will occur on either side of a surface cold front initially analyzed from the Hampton Roads area southwestward across central NC, northwestern SC, northern GA, west-central AL, southwestern MS, central LA, and the TX Gulf Coastal Plain. ....Portions of coastal southern CA... Over Pacific waters, where moisture and buoyancy should be greatest, a few mini-supercells (with or without lightning) will pose a threat for waterspouts, and perhaps a small tornado moving ashore for any such activity that persists to the coastline. A couple cells with modest rotation already have been observed over water, with more possible through the day. Cooling aloft related to the mid/upper cyclone will spread southward down the coast, steepening midlevel lapse rates atop a regime of low-level moisture advection, and supporting potential for isolated thunderstorms. Favorable vertical shear is spreading across the area already, with enlarged low-level hodographs evident in VWP data and persisting/enlarging further in time series of forecast soundings. Most of the surface-based buoyancy will remain over the Pacific, briefly impinging on immediate coastal areas, with MLCAPE in the 50-250 J/kg range. CAPE will struggle to reach into ideal icing layers for lightning generation, though the updraft enhancement via internal vertical pressure-gradient forces may help lightning potential in rotating/deeper cells. ...Edwards/Kerr.. 02/24/2023 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .